The aforesaid error Failed to fetch Tally data appears if the Tally License Server and Tally Software both are running on the same Port.

Solution :-
1) In Tally Software, press F12 and select option Advanced Confiuration
2) Next, set the Port to a different than the current Port, say 9001 or 9002.
3) Save it using Ctrl+A. The new Port settings will be visible in the Gateway of Tally.
4) Next, start UDIMagic and in the 2nd screen, click on the Settings button and set the Port as assigned in Tally Software in point 2.
5) Next, in UDIMagic 3rd screen, click on the "Test Connection" button to test connection with Tally Software.